Sugar-powered nanoantimicrobials for combating bacterial biofilms.

Bacterial biofilms cause chronic infections due to their inherent tolerance to antimicrobial therapies. We describe and compare the efficacy of two types of sugar (d-glucose and d-mannose)-modified cyclodextrin nanocarriers (CD-GLU and CD-MAN) loaded with antibacterial agents for preventing and eradicating bacterial biofilm. The antibacterial agents comprise a quorum sensing inhibitor (5,6-dimethyl-2-aminobenzimidazole, DMABI) and two antibiotics (erythromycin and rifampicin), and the cyclodextrin nanocarriers were tested on Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive).

The Acinetobacter baumannii Two-Component System AdeRS Regulates Genes Required for Multidrug Efflux, Biofilm Formation, and Virulence in a Strain-Specific Manner.

The opportunistic pathogen Acinetobacter baumannii is able to persist in the environment and is often multidrug resistant (MDR), causing difficulties in the treatment of infections. Here, we show that the two-component system AdeRS, which regulates the production of the AdeABC multidrug resistance efflux pump, is required for the formation of a protective biofilm in an ex vivo porcine mucosal model, which mimics a natural infection of the human epithelium. Interestingly, deletion of adeB impacted only on the ability of strain AYE to form a biofilm on plastic and only on the virulence of strain Singapore 1 for Galleria mellonella RNA-Seq revealed that loss of AdeRS or AdeB significantly altered the transcriptional landscape, resulting in the changed expression of many genes, notably those associated with antimicrobial resistance and virulence interactions.

Sugar-Grafted Cyclodextrin Nanocarrier as a "Trojan Horse" for Potentiating Antibiotic Activity.

Purpose: The use of "Trojan Horse" nanocarriers for antibiotics to enhance the activity of antibiotics against susceptible and resistant bacteria is investigated.

Methods: Antibiotic carriers (CD-MAN and CD-GLU) are prepared from β-cyclodextrin grafted with sugar molecules (D-mannose and D-glucose, respectively) via azide-alkyne click reaction. The sugar molecules serve as a chemoattractant enticing the bacteria to take in higher amounts of the antibiotic, resulting in rapid killing of the bacteria.

Bifunctional Coating with Sustained Release of 4-Amide-piperidine-C12 for Long-Term Prevention of Bacterial Colonization on Silicone.

Bacterial colonization by nosocomial pathogens on medical device surface can cause serious and life-threatening infections. We showed that 4-amide-piperidine-C12 (4AP12), the base form of 4-dodecaneamidepiperidine HCl, has broad-spectrum antimicrobial activity against both Gram-negative and Gram-positive bacteria and fungi. Resistance assay confirmed that prolonged exposure of bacteria to subinhibitory concentrations of 4AP12 did not induce resistance to 4AP12.

Disruption of biofilm formation by the human pathogen Acinetobacter baumannii using engineered quorum-quenching lactonases.

Acinetobacter baumannii is a major human pathogen associated with multidrug-resistant nosocomial infections; its virulence is attributed to quorum-sensing-mediated biofilm formation, and disruption of biofilm formation is an attractive antivirulence strategy. Here, we report the first successful demonstration of biofilm disruption in a clinical isolate of A. baumannii S1, using a quorum-quenching lactonase obtained by directed evolution; this engineered lactonase significantly reduced the biomass of A.

A method for generating marker-less gene deletions in multidrug-resistant Acinetobacter baumannii.

Background: Acinetobacter baumannii is an important nosocomial pathogen that has become increasingly resistant to multiple antibiotics. Genetic manipulation of MDR A. baumannii is useful especially for defining the contribution of each active efflux mechanism in multidrug resistance.

N-Octanoylhomoserine lactone signalling mediated by the BpsI-BpsR quorum sensing system plays a major role in biofilm formation of Burkholderia pseudomallei.

The genome of Burkholderia pseudomallei encodes three acylhomoserine lactone (AHL) quorum sensing systems, each comprising an AHL synthase and a signal receptor/regulator. The BpsI-BpsR system produces N-octanoylhomoserine lactone (C8HL) and is positively auto-regulated by its AHL product. The products of the remaining two systems have not been identified.

Synthesis of cyclic di-nucleotidic acids as potential inhibitors targeting diguanylate cyclase.

Five analogs of cyclic di-nucleotidic acid including c-di-GMP were synthesized and evaluated for their biological activities on Slr1143, a diguanylate cyclase of Synechocystis sp. Slr1143 was overexpressed from the recombinant plasmid which contained the gene of interest and subsequently purified by affinity chromatography. A new HPLC method capable of separating the compound and product peaks with good resolution was optimized and applied to the analysis of the compounds.

CdpA is a Burkholderia pseudomallei cyclic di-GMP phosphodiesterase involved in autoaggregation, flagellum synthesis, motility, biofilm formation, cell invasion, and cytotoxicity.

Cyclic diguanylic acid (c-di-GMP) is an intracellular signaling molecule involved in regulation of cellular functions such as motility, biofilm formation and virulence. Intracellular level of c-di-GMP is controlled through opposing diguanylate cyclase (DGC) and phosphodiesterase (PDE) activities of GGDEF and EAL domain proteins, respectively. We report the identification and characterization of cdpA, a gene encoding a protein containing an EAL domain in the Gram-negative soil bacillus and human pathogen Burkholderia pseudomallei KHW.

Growth-related changes in intracellular spermidine and its effect on efflux pump expression and quorum sensing in Burkholderia pseudomallei.

The Burkholderia pseudomallei BpeAB-OprB resistance-nodulation-division (RND) family pump effluxes aminoglycoside and macrolide antibiotics as well as acylhomoserine lactones (AHLs) involved in quorum sensing. Expression of bpeA-lacZ was cell density-dependent and was inducible in the presence of these compounds. Intracellular levels of spermidine and N-acetylspermidine increased with cell density in wild-type B.

A role of Burkholderia pseudomallei flagella as a virulent factor.

Burkholderia pseudomallei is an agent of melioidosis and is closely related to avirulent B. thailandensis. Burkholderia thailandensis has a 15-bp deletion within the variable region of the flagellin gene fliC compared with B.

A multigene family of Heteractis magnificalysins (HMgs).

Sea anemones are passive predators. They use their specialized stinging cells (nematocysts) to immobilize any prey that blunders into them. A cnida fires, everting a tubule which delivers toxins that may stick to a prey.

Control of quorum sensing by a Burkholderia pseudomallei multidrug efflux pump.

The Burkholderia pseudomallei KHW quorum-sensing systems produced N-octanoyl-homoserine lactone, N-decanoyl-homoserine lactone, N-(3-hydroxy)-octanoyl-homoserine lactone, N-(3-hydroxy)-decanoyl-homoserine lactone, N-(3-oxo)-decanoyl-homoserine lactone, and N-(3-oxo)-tetradecanoyl-homoserine lactone. The extracellular secretion of these acyl-homoserine lactones is dependent absolutely on the function of the B. pseudomallei BpeAB-OprB efflux pump.

Synergistic interaction between phenothiazines and antimicrobial agents against Burkholderia pseudomallei.

The gram-negative soil bacillus Burkholderia pseudomallei is the causative agent of melioidosis, a severe and potentially fatal septicemic disease that is endemic to Southeast Asia and northern Australia. Its intrinsic resistance to many antibiotics is attributed mainly to the presence of several drug efflux pumps, and therefore, inhibitors of such pumps are expected to restore the activities of many clinically important antimicrobial agents that are the substrates of these pumps. The phenothiazine antipsychotic and antihistaminic drugs prochlorperazine, chlorpromazine, and promazine have a synergistic interaction with a wide spectrum of antimicrobial agents, thereby enhancing their antimicrobial potency against B.

Method for regulated expression of single-copy efflux pump genes in a surrogate Pseudomonas aeruginosa strain: identification of the BpeEF-OprC chloramphenicol and trimethoprim efflux pump of Burkholderia pseudomallei 1026b.

Construction and integration of recombinant mini-Tn7 expression vectors into the chromosome of a surrogate, efflux-sensitized, and biosafe Pseudomonas aeruginosa host was validated as a generally applicable method for studies of uncharacterized bacterial efflux pumps. Using this method, the Burkholderia pseudomallei bpeEF-oprC operon was shown to encode a chloramphenicol and trimethoprim efflux pump.

The Burkholderia pseudomallei BpeAB-OprB efflux pump: expression and impact on quorum sensing and virulence.

BpeAB-OprB is a multidrug efflux pump of the bacterial pathogen Burkholderia pseudomallei and is responsible for conferring antimicrobial resistance to aminoglycosides and macrolides. Expression of bpeAB-oprB is inducible by its substrate erythromycin and upon entry into stationary phase. BpeR, a member of the TetR family, functions as a repressor of the bpeAB-oprB operon.

Cloning and molecular characterization of the first aquatic hyaluronidase, SFHYA1, from the venom of stonefish (Synanceja horrida).

We report here for the first time the molecular characterization of a hyaluronidase from an aquatic source. SFHYA1 is the hyaluronidase found in the venom gland of stonefish, Synanceja horrida. Using a cDNA segment amplified with degenerate oligonucleotides based on the amino acid sequences of a conserved region in testicular-type hyaluronidases and a tryptic fragment of SFHYA1, clones encoding the precursor of this enzyme were isolated from a cDNA library prepared from stonefish venom glands.

Modified virulence of antibiotic-induced Burkholderia pseudomallei filaments.

Melioidosis is a life-threatening bacterial infection caused by Burkholderia pseudomallei. Some antibiotics used to treat melioidosis can induce filamentation in B. pseudomallei.

The BpsIR quorum-sensing system of Burkholderia pseudomallei.

BpsIR, a LuxIR quorum-sensing homolog, is required for optimal expression of virulence and secretion of exoproducts in Burkholderia pseudomallei. Cell density-dependent expression of bpsI and bpsR, the positive regulation of bpsIR expression by BpsR, and the synthesis of N-octanoyl-homoserine lactone (C8HSL) by BpsI are described in this report.

Development of an ELISA using a recombinant 41 kDa partial protein (P45N') for the detection of Riemerella anatipestifer infections in ducks.

Riemerella anatipestifer, a gram-negative bacillus, is the causative agent of duck septicemia, a disease which could incur much economic loss in the duck industry. An indirect enzyme-linked immunosorbent assay (ELISA) has been developed to facilitate early detection of R. anatipestifer infection in ducks.

Characterization of Burkholderia pseudomallei infection and identification of novel virulence factors using a Caenorhabditis elegans host system.

The environmental saphrophyte Burkholderia pseudomallei is the causative agent of melioidosis, a systemic, potentially life-threatening condition endemic to many parts of south-east Asia and northern Australia. We have used the soil nematode Caenorhabditis elegans as a model host to characterize the mechanisms by which this bacterium mounts a successful infection. We find that C.

Identification and characterization of CAMP cohemolysin as a potential virulence factor of Riemerella anatipestifer.

Riemerella anatipestifer is responsible for exudative septicemia in ducks. The genetic determinant of the CAMP cohemolysin, cam, from a strain of R. anatipestifer was cloned and expressed in Escherichia coli.